Peasants got off easy; the thatch roof on your typical hovel is relatively easy on the brain pan. Pity the royals, the heavy timbers and stone blocks of their great houses hurt when they hit you.

Then again, I suspect that these sorts of exercises are generally applicable to any number of potential real or imagined mass-casualty events. A large gas explosion or terrorist attack that pancakes one or more buildings, Godzilla visiting downtown, earthquake (unlikely as that may be), or tidal wave all share a common array of issues.

Including:
A large number of confused and disoriented people who have few resources and are subject to panic and making the situation worse. People who need to be reoriented, brought up to speed, protected, provided minimum levels of food, water, shelter, medical care.

A number of people trapped or isolated under debris. People who need to be located and rescued.

Fracturing of infrastructure. Roads are blocked, power is lost, water mains lose pressure, communications systems fail or get overloaded.

Then there are secondary disasters. Damaged gas and power lines cause fires to spring up. Sewage and water mains can cause flooding, undermine roads and cause otherwise sound buildings to collapse.

Of course, all of this is secondary to getting responders mobilized and organized. They can't help anyone without being organized. A lot of official exercises justifiably focus on setting up a durable, redundant command, communication and coordination system. Setting up an effective chain of command across responder systems. Doing it when key people are disabled or out of communication.

Major problems can center around something as simple as people not knowing what radio frequencies/channels to turn to, and failure to using common terminology.